Saito Hiraga is the main male protagonist of the anime, light novel and manga series, The Familiar of Zero. He is transported from his home in Tokyo, Japan to the magical world of the kingdom of Tristain and becomes the Familiar to Louise, acquiring the power of "Gandolf", the Magical protector to a Void Mage. Saito later becomes a Knight, thereby becoming an official Noble and also becomes the Vice-Captain of the Undine Knights. He is also the main love interest of Louise Françoise Le Blanc de La Vallière.
Saito comes from our world, but was summoned from to Louise's world to be Louise's familiar. At first Louise and Saito did not get along and Louise treated him quite poorly. But as the series progresses, the two eventually come to understand each other and fall in love. Whenever Saito pays any attention to another girl, especially her chest, Louise is quick to punish him. In the anime, Saito's punishment is usually a whipping from Louise's riding crop, a blast from her void explosion spell, or sometimes he is kicked in the crotch by Louise.
Louise is the main female protagonist of The Familiar of Zero and is the main love interest of Saito. In the beginning of the second year at the Tristain Academy of Magic, the second year students were reacquired to perform a sacred and special ritual to summon a Familiar, a magical protector and partner. Louise began the ritual, hoping to gain a strong and powerful magical Familiar to impress her classmates, but became completely distraught and angered when she summoned Saito, an ordinary boy from an alternate world. Saito was confused by his new surroundings, unable to understand the language and overall believed that Louise and the students were weird and crazy. Louise refused to accept Saito as her Familiar and wanted to redo summoning the spell, seeing it was unheard of to have a "peasant boy" be a magical Familiar. However, since the ritual was sacred her request was refused and upon being threatened to be expelled from the Academy, Louise had no choice, but to accept the situation. Louise then proceed to complete the ritual and she and Saito shared their first romantic kiss as it was the reaqcuirement needed to officially complete the ceremony, much to her embrassment and Saito's confusion. By kissing Saito, he had offically become Louise's Familiar and rune of the Familiar had appeared on Saito's hand.
However, Louise and Saito soon found difficulty in their newfound Familiar and master relationship as Saito strongly wished to return home and Louise was unable to understand or handle the noise he made. She attempted to silence him with her magic, but instead was able to allow her and Saito to understand and commincate with each other. Saito was properly explained of the situation, but was unable to accept the situation and still wanted to return home, attempting to runaway, but was stopped with help from Louise's classmates. Saito had no choice but to accept his situation, but the relationship between him and Louise had made no improvements. Louise hated she had summon a peasant boy to act as her Familiar, treated Saito with no respect and disregarded his feelings and ultimately treated Saito as a servant boy, forcing him to dress her, wash her clothes and sleep on a pill of hay. Upon being angered or refused, Louise decided to harm Saito with her explosion spells and hitting him with a riding crop. Saito strongly disliked Louise, seeing she had a terrible temper, selfish, arrogant, stuck up, and proud. Saito continued to be upset with her treatment towards him, treating him like a dog and was further upset that she refused to believe his claims that he was from an alternate world. Saito stands up to Louise, but is forced to listen and obey her wishes when she threatens to starve him.
During their time together, Saito soon began to learn more about Louise, discovering her inability to use any magic whatsoever and the nickname given to her by her classmates, "Louise the Zero". While Saito teased Louise with the knowledge, he began to understand and sympathise with her feelings, learning that although she appears to have a strong exterior, she overall is deeply hurt and saddened by her classmates bullying. Saito also discovers that Louise does have a kind heart, revealed after his fight with Guiche that she nursed him back to health for several nights and days and even acquired a expensive medicine to help him. Saito also revealed that he thinks Louise is both beautiful and cute, but still has trouble with her personality. In return, Louise begins to better understand Saito and slowly begins to treat him more better. Upon witnessing his incredible sword and fighting skills through his power as Gandolf, Louise comes to better appreciate Saito and finds him to be a better Familiar than she originally expected. Louise also begins to believe Saito's claims of him being from an alternate world, finding objects such as rocket launcher and a jet plane, thus proving he is telling the truth.
Louise and Saito slowly begin to form a better relationship, greatly improving as time passes upon learning and understanding each other better and both begin to grow more closer. However, unknown to either of the them, both Saito and Louise begin to develop romantic feelings for each other and later come to realize they have deeply fallen in love. Louise and Saito begin to share several romantic moments together as time passes as Saito saves Louise when she is attacked and they both even share a special romantic dance together, making their feelings grow more stronger. Louise also starts to become incredibly jealous when Saito begins receiving the attention of many admirers, specifically her classmate, Kirchie and maid, Siesta, causing her jealousy to act on her anger and becomes violent with Saito. However, Louise and Saito deny their romantic feelings when confronted. Louise still thinks of her Noble status as it's uncommon for a noble and peasant to be together and Saito denies his feelings for Louise due her personality. Despite their denial, everyone slowly starts to become aware of their romance and Saito's magical sword Derflinger occasionally confronts Saito about his love for Louise.
Eventually towards the ending of the first season, Saito and Louise finally begin to realize and acknowledge they are in love with each other. During a mission for Princess Henrietta, they were tasked to retrieve an important message she sent to her cousin and secret lover, Prince Wales in regards to arranged marriage between Henrietta and a ruler of a neighbouring kingdom. In order to help with their mission, Louise and Saito gained the assistance of Lord Wards, Leader of the Magic Griffin Squad as well as revealed to be Louise's fiancé. Saito was shocked of the revelation and became jealous of the arrangement between Louise and Wards, bearly speaking a word to either Wards or Louise since beginning the mission and was almost non responsive, much to Louise's annoyance. During this time, both Louise and Saito became conflicted with their feelings and soon when Lord Wards revealed his desire to marry Louise once the mission is completed, he learns that Louise is in love with Saito and vows to win her love by the end of the mission. Eventually the situation worsened when Saito's ability to protect Louise was called into question when Saito was beaten in a duel between him and Lord Wards.
Siesta is a maid at the Tristain Academy of Magic and is the second person to fall in love with Saito and is Louise's first rival to win his affections. Since meeting Siesta, Saito and Siesta immediately develop a close friendship and relationship and begin spending a lot of time together. Saito and Siesta find they have much in common, discovering that Siesta is actually part Japanese as her grandfather originally came from Saito's home world. They enjoy each other's company as Saito reveals to Siesta much about his life in Japan and she becomes the first person to believe him his claims while others originally didn't. Saito and Siesta are protective of each other as Saito rescued Siesta when she was forced to become the mistress to Count Mott or when Siesta offered him a sleeping potion to avoid an upcoming battle.
Originally in the beginning of the series, Saito begins to develop romantic feelings for Siesta, seeing she is a kind, caring and shy person and views her to be a breath of fresh air and relief due to him having a hard time being with Louise in the beginning of the series. Siesta soon begins to fall in love with Saito, but is rather shy in expressing her feelings, but can become jealous when she sees him with other girls. While Saito finds Siesta attractive, he slowly begins to lose his romantic feelings, upon realising he has deeply fallen in love with Louise. Despite Saito realising his true love for Louise, Siesta remains determined to win him for herself and as the series progresses, she starts to become more romantically aggressive, bold and determined to win Saito's love and affections.
Kirchie is a highly well known flirtatious student at the Tristain Academy of Magic, specialising in the fire element of magic.
Henrietta is the Princess of the Magical Kingdom of Tristain and is childhood friends with Louise. Originally at the beginning of the series, Henrietta has been in a secret long-time romantic relationship with her cousin, Prince Wales of Albion and she and Saito are acquientices, only knowing each other through their respective relationships with Louise. Henrietta comes to trust and rely on Saito and requests him and Louise go on a secret mission to send a message to Prince Wales. However, Henrietta becomes heartbroken when Wales is murdered and grieves his death until he mysteriously returns in the beginning of the second season, claiming his double was killed and has been in hiding ever since. However, unknown to Henrietta, Wales was given false life upon being revived by Cromwell's Ring of Andavari and was under his control for the purpose to kidnap and manipulate Henrietta upon discovering their romance. Wales was defeated by Saito and Louise and was freed of his mind control, but sadly Wales dies once again in Henrietta's arms, but not before assuring and encouraging Henrietta to move on with her life and find new love. Since then, Henrietta begins to develop a more closer relationship with Saito and eventually she falls in love with him.
Tabitha is a student at the Tristain Academy of Magic. Tabitha is a emotionless, quiet and calm person who speaks with very few words.